1. Field of the Invention
The present invention relates to a stencil printing machine in which a stencil sheet wound on a stencil drum is pressed against a opposite which is located close to the stencil sheet, like a press of the internal pressing type, in order to perform stencil printing process.
2. Description of the Related Art
Existing stencil printing machines includes, for example, a type which is equipped with an internal pressing mechanisms. FIG. 1 is a schematic diagram representatively showing one example of the stencil printing machines of the prior art internal pressing type.
As illustrated in the same figure, the prior art stencil printing machine is composed of a printing mechanism 4 having a stencil drum 16 and a opposite 17 which are located with their external peripheral surfaces being close to each other inside of a machine body 50, a paper feed mechanism 5 serving to feed paper 22 as placed on a paper feed tray 23 to the printing mechanism 4, and a sheet discharge mechanism 6 serving to the printed paper 22 to a sheet discharge tray 34.
The stencil drum 16 as described above is provided with a stencil sheet wound on the external peripheral surface thereof. The stencil drum 16 is designed to be detachable from the machine body 50 in order that another stencil drum can substitute therefor in accordance with a desired color and so forth and that the stencil drum as detached can be used in another stencil printing machine.
Also, the stencil drum 16 is provided with an internal pressing roller 47 therein for outwardly pressing the internal peripheral surface of the stencil drum 16. The internal press roller 47 is linked with a printing press motor 48 through a spring 49 in order that the driving power of the printing press motor 48 is transmitted to the internal press roller 47 through the pressing force of the spring 49 to control the pressing force of the internal press roller 47 toward the internal peripheral surface of the stencil drum 16. The printing press motor 48 is driven by making use of a directive pulsed signal as selected. The pressing force of the internal press roller 47 can therefore be controlled by adjusting the directive pulsed signal.
In accordance with the configuration of such a conventional stencil printing machine, therefore, the external peripheral surface of the stencil drum 16 is moved together with the external peripheral surface of the opposite 17 located close thereto in the same direction during the rotation thereof, while the stencil sheet wound on the stencil drum 16 is pressed against the paper 22 passing between the stencil drum 16 and the opposite 17 by driving the printing press motor 48 in accordance with the directive pulsed signal as selected, so that an image formed on a stencil sheet is printed onto the paper 22 in accordance with the stencil printing mechanism.
However, in the case of the conventional stencil printing machine as described above, the respective stencil drum and the respective machine body can be endued with dispersed characteristics due to the dispersion of the accuracy of setting the stencil drum 16 and the printing mechanism 4 and so forth.
Accordingly, in the case that another stencil drum can substitute for the stencil drum 16 or that the stencil drum 16 as detached is used in another stencil printing machine as described above, a desired pressing force can no longer be obtained, even when the printing press motor 48 is driven with the same directive pulsed signal because of the dispersion of the characteristics as described above, resulting in dispersion of printed images whose densities become sometimes low and sometimes high.
Namely, for example, in the case that the stencil drum 16 is replaced with a stencil drum 16xe2x80x2 as illustrated in FIG. 3, the pressing force against the stencil drum 16xe2x80x2 deviates from a desired value due to an error dxcex8 in the driving angle of the internal press roller 47 so that the image as printed with the stencil drum 16xe2x80x2 is different than that as printed with the stencil drum 16 because of the differential accuracy of setting the stencil drums.
The present invention has been made in order to solve the shortcomings as described above. It is an object of the present invention to provide a stencil printing machine capable of preventing the printing quality of images from being dispersed due to the dispersion of the accuracy of setting the respective stencil drums and the like.
In order to solve the problems as described above, a stencil printing machine recited in claim 1 comprises a stencil drum and a opposite which are a pair of cylindrical parts located with their external peripheral surfaces being close to each other, a stencil sheet being detachably wound on the external peripheral surface of said stencil drum, and serving to perform stencil printing process by rotating said stencil drum and said opposite in order that the external peripheral surfaces thereof are located close to each other and moved in the same direction while said stencil sheet is pressed against said opposite, and by making said stencil sheet in contact under pressure with a sheet of paper passing between said stencil drum and said opposite by the pressing force of said stencil drum, wherein said stencil drum is detachably mounted on said stencil printing machine and provided with a storage unit for storing information about the pressing force of said stencil drum against said opposite.
In accordance with the present invention as recited in claim 1, it is possible to prevent the pressing force from varying due to dispersed characteristics of the stencil drums which are caused by the dispersion of the accuracy of setting the stencil drum and so forth. Namely, the information about the respective pressing forces of the respective stencil drum is stored in the storage unit provided for the respective stencil drum and is used for adjusting the printing press as applied. It is therefore possible to prevent printed images from being lightened or darkened.
Also, a stencil printing machine recited in claim 2 comprises a stencil drum and a opposite which are a pair of cylindrical parts located with their external peripheral surfaces being close to each other, a stencil sheet being detachably wound on the external peripheral surface of said stencil drum, and serving to perform stencil printing process by rotating said stencil drum and said opposite in order that the external peripheral surfaces thereof are located close to each other and moved in the same direction while said stencil sheet is pressed against said opposite, and by making said stencil sheet in contact under pressure with a sheet of paper passing between said stencil drum and said opposite by the pressing force of said stencil drum, wherein said stencil drum is detachably mounted on said stencil printing machine and wherein a machine body of said stencil printing machine is provided with a storage unit for storing information about the pressing force of said opposite against said stencil drum.
In accordance with the present invention as recited in claim 2, it is possible to prevent the pressing force from varying due to dispersed characteristics of the stencil printing machines which are caused by the dispersion of the accuracy of setting the printing mechanism of the stencil printing machine and so forth. Namely, the information about the respective pressing forces of the respective stencil printing machines are stored in the storage unit provided for the respective stencil printing machines and is used for adjusting the printing press as applied. It is therefore possible to prevent the qualities of the printed images from being dispersed.
Furthermore, in accordance with the present invention as recited in claim 3, a stencil printing machine recited of claim 2 further comprises a standard pressing force determination unit for determining a standard pressing force; a correction value calculation unit for calculating a correction value by the use of the information about the pressing force as stored in said stencil drum and the information about the pressing force as stored in said machine body; and a calculation unit for calculating the pressing force by the use of said standard pressing force and said correction value.
In accordance with the present invention as recited in claim 3, while standard pressing forces are determined, the correction is conducted by the use of the correction values calculated with respect to the standard pressing forces for the respective stencil printing machines and the respective stencil drums. It is therefore possible to prevent the printing press as applied from being dispersed due to the dispersion of the characteristics of the individual stencil printing machines and the individual stencil drums even when an arbitrary combination of one of the stencil printing machines and one of the stencil drums is used.